Outdoor pools are often covered with a safety pool cover during the winter months when they go unused. Covering a pool obviates the need to maintain the pool during the winter and protects the pool from the harsh conditions of winter. In use, safety pool covers prevent debris and other foreign objects from entering the pool water and have the necessary strength to prevent a person from falling into the pool.
To prevent algae growth in the pool when covered, it is preferable that pool covers be made from a fabric that prevents as much sunlight as possible from penetrating through the pool cover fabric and into the water below. Traditional pool covers were made from a woven fabric that was coated with a plastic material, such as polyvinylchloride. The resulting fabric was UV resistant to block sunlight and thereby prevent algae growth under the pool cover. However, the cover was also solid in that it was impermeable to fluid and moisture. Mechanical drains were incorporated into the covers else, when it rained, water would collect on top of the cover and the pool cover would tend to sag under the weight of the collected water. However, the drains oftentimes would clog with debris, rendering them ineffective for drainage purposes.
To combat these problems, pool covers began being made from single-layer, woven, uncoated fabrics. These fabrics allowed water to flow through the apertures in the cover and thus prevented water collection on top of the cover. However, because these fabrics were not solid, just as water was allowed to pass through the fabric so too was sunlight. Thus, these fabrics were less capable of blocking sunlight and preventing algae growth.
Traditionally, the more water flow the pool cover allowed (i.e., the more apertures that are provided in the fabric or the larger the size of the apertures provided in the fabric), the less capable the pool cover was at blocking light and thus preventing algae growth. For example, U.S. Pat. No. 6,886,187 to Zell et al. discloses a pool cover made from a single-layer woven fabric that purportedly blocks 100% sunlight. Yet the disclosed fabric provides a flow rate of water of only 0.1 to 5 gallons per square foot per minute. There remains a need for a woven fabric for pool covers that successfully blocks sunlight (preferably up to 100%) and provides for higher water flow through the pool cover.